多孔催化剂有效因子的近似分析解(Ⅱ)近似分析解与数值解的比较

根据本文第Ⅰ部分所提出的多孔催化剂有效因子近似计算式,针对不同形式的幂函数型动力学方程和双曲型动力学方程,计算了等温下Thiele模数不同时非一级反应的有效因子,并且用数值方法求出相应条件下的有效因子以作比较.大量的计算结果证明所提出的近似计算式较之文献上已有的近似式,不但精度高,而且适用范围广.同时近似式中参数估值简便,克服了以往研究者所提出的式子中这方面所存在的困难.     

计算多孔催化剂有效因子的区域分割法

提出了计算多孔催化剂颗粒有效因子的区域分割法,将整个一维区间划分为几个子区间,然后在每个子区间内用一点配置法求解非线性扩散-反应问题.采用区域分割法,针对三种不同形状的催化剂颗粒,对幂函数型动力学方程和双曲型动力学方程进行了大量的计算.所得的计算结果与正交配置解吻合.区域分割法的优点是使用简便、计算快速.采用区域分割法还可以计算催化剂颗粒死区半径,所得计算结果合理.     

多孔固体催化剂的内扩散有效因子

本文以国内学者的研究成果为重点,对催化剂扩散有效因子的研究进行了综述,介绍了催化剂内扩散有效因子研究的基本内容及发展趋势,着重论述了简化方法、数值积分打靶法、正交配置法等对不同反应体系有效因子计算的应用 。     

圆柱形催化剂等温有效系数的近似解析解

多孔催化剂有效系数的计算,无论在催化剂工程设计的理论研究中还是在实际应用中,都是十分重要的。近二十年来,人们用各种不同的方法求解催化剂的有效系数。这方面的情况,我们已经在另一篇文章中进行过综述,本文不再详述。本文引入等效温度的概念,从物理上寻求催化剂有效系数的近似解析解。我们曾在以前几篇文章中谈到了利用等效温度法计算球催化剂的有效系数、本文则是将等效温度法应用于园柱形催化剂的有效系数的计算,并将n=0.5,n=1.5,n=2.0,n=2.5等四种情况下所获得的计算结果与计算机数值解进行了比较。结果表明,利用等效温度法求解催化剂的有效系数不仅大大简化了计算过程,而且计算的精度也比较高。     

多孔催化剂效率因子的多组分扩散模型(VI)近似解析法求解二维模型

着眼于直接计算圆柱状催化剂效率因子的二维模型,进行了两方面的工作：发展合适的近似解析法并检验该方法的可靠性．在近似解析法中,以多项式关联效率因子和Thiele模数（φ）,并结合二维问题的特征,选择（1／tanh∮-1／φ）／φ为多项式元素．通过极端情况下二维反应-扩散方程的求解,提供了使用该方法所需参数的实际数值．在一级可逆反应、变换反应和催化剂表面中毒的甲醇分解反应3种场合下考察本文所提出的近似解析法,所得结果表明：该方法不仅计算过程极其简单,而且结果可靠,其计算精度与有限元法和正交配置法相当．该方法对表面中毒情况的计算同样适应．     

反应条件下多孔催化剂上有效扩散系数及曲节因子的分析计算

采用CDS－810微反系统,在实验条件为：常压、氢苯比3.0-8.0、温度363.15K-453.15K时,进行了在四种不同粒度Ni/Al2O3催化剂上的气相苯加氢反应,利用实验数据计算了不同反应组成、不同反应速率时苯的有效扩散系数、反应死区及催化剂的曲节因子。计算结果表明：有效扩散系数不随反应速率改变,多孔催化剂的曲节因子可以看作多孔催化剂的结构参数,不随反应条件变化。     

多孔催化剂效率因子的多组分扩散模型(Ⅲ)——加压下WB-2中温变换催化剂的效率因子

在内循环无梯度反应器中研究37×10~5Pa(表)及13×10~5Pa(表)压力下工业粒度ф9×7mm.WB-2中温变换催化剂的宏观反应速率,测试了催化剂的孔径分布和曲节因子.本报应用常压下测得的本征动力学方程,对于十七组宏观实验速率,按照前报(Ⅱ)提出的简化多组分扩散模型,求取了效率因子的数值解,并与实验观察值作了比较.比较的结果令人满意.本报由此认为,对于中温变换这类压力不高的反应,研究其加压宏观动力学行为,不必进行加压宏观速率的实验测定.加压下的效率因子及宏观反应速率可在常压测得的本征动力学基础上借助本文提出的模型计算求得.     

多孔催化剂效率因子的多组分扩散模型 (Ⅱ)B109中温变换催化剂的效率因子

按照本文(Ⅰ)中提出的多孔催化剂效率因子的多组分扩散模型及其数值计算方法,本报计算了B109中温变换催化剂的效率因子,并与实验测定值进行了比较.测试了B109变换催化剂的孔隙率、孔径分布、曲节因子和常压下的本征动力学,并在内循环无梯度反应器中测试了常压下φ9.8×8.3mm圆柱状颗粒B109催化剂于各种气体组成和温度条件下只计入内扩散过程的宏观反应速率.由此获得十六种情况下效率因子的实验观察值为0.142至0.455,相同反应条件下模型预计值与实验观察值的相对误差为-0.25至0.06.比较的结果令人满意.     

多孔固体催化剂有效系数的计算

现代化学工业和炼油工业中广泛应用各式各样的多相催化反应器。固体催化剂通常都具有多孔性结构,在颗粒内部形成比较其外表而火得多的内表面,促使表面化学反应加速进行,同时发生在流体主体和颗粒外表面之间的外扩散过程以及在颗粒内部的内扩     

多孔固体催化剂的有效导热系数

建立了测定多孔固体催化剂骨架导热系数的实验装置和由此计算催化剂有效导热系数的简化方法，测定并计算了若干工业过程催化剂的有效导热系数，同时，计算了甲烷蒸汽转化催化剂的非等温效率因子。     

Approximate Analytical Solutions of Biofilm Reactor Problem in Applied Biotechnology

Theoretical Foundations of Chemical Engineering - Dueck’s mathematical model of biofilm is discussed. This model is also generalized to cover all substratum types. This system is based on a...     

多孔催化剂效率因子的多组分扩散模型 (Ⅰ)多组分扩散模型及数值计算方法

本文按多孔催化剂内多组分分子扩散及努森扩散联合过程的特性,导出了描述等温球形催化剂内单一反应的反应物和产物浓度分布的二阶非线性常微分方程组.微分方程中各个反应组分的浓度梯度强烈相互耦合.在计算机上用打靶法求解此常微分方程组提出的两点边值问题,即可求得各个反应组分的浓度分布和催化剂效率因子的数值解.由于反应组分的有效扩散系数间的差异,催化剂内反应组分的组成变化之间的关系不再符合反应的化学计量关系.当内扩散过程的阻滞作用严重时,催化剂颗粒内会出现“死区”,死区内反应组分的浓度趋近于平衡浓度,实际上不再继续进行反应.存在死区时,使用此数学模型及解题方法可求出死区的半径及此情况下催化剂的效率因子.工业上常用的圆柱状催化剂按照相等比外表面积的球体处理.     

一种新型的生化需氧量分析装置

介绍一种新型的生化需氧量分析装置,不但能准确地测定环境水质的生化需氧量值,且测定过程更是一种与实际微生物生化降解过程相似的供氧“呼吸”过程。根据这个过程绘制的反应整个生化过程中每个时刻生化降解情况的曲线,能给环境工作者提供更为直观、详细、可靠、有效的数据。     

Reusable Gold(I) Catalysts with Unique Regioselectivity for Intermolecular Hydroamination of Alkynes

Two gold(I) phosphine complexes bearing the low‐coordinating bis(trifluoromethanesulfonyl)imidate ligand, namely AuSPhosNTf₂ and AuPPh₃NTf₂, are active catalysts for the regioselective intermolecular hydroamination of both internal and terminal alkynes under mild reaction conditions. The catalysts show a regioselectivity based on electronic rather than steric factors, which allow the preferential synthesis of regioisomers opposite to those described previously. This subtle chemo‐ and regioselectivity depends on the catalyst, substrates and reaction conditions employed, and allows one to perform new tandem reactions. These gold(I) complexes operate under free‐solvent conditions, without exclusion of air, without addition of acidic promoters and can be quantitatively recovered and reused by simple precipitation in hexane.     

光滑圆管中恒定物性流体的对流传热准数方程近似分析解

本文从动量,能量及质量连续微分方程式出发,结合有关涡流扩散系数关联式及传热涡流混合长与动量涡流混合长之比的关联式,用积分的方法解出努歇特准数(Nusselt Number)的分析解表达式.本公式与彼德柯夫(Petukhov)用数值解方法得出的努歇特准数关联式比较,最大偏差小于7%.本公式的贡献在于能用一个公式计算各种鲁兰特准数和10~4以上各种雷诺准数条件下的圆管中湍流传热的努歇特准数.     

FI Catalysts: A New Family of High Performance Catalysts for Olefin Polymerization

This paper reviews a new family of olefin polymerization catalysts. The catalysts, named FI catalysts, are based on non‐symmetrical phenoxyimine chelate ligands combined with group 4 transition metals and were developed using “ligand‐oriented catalyst design”. FI catalysts display very high ethylene polymerization activities under mild conditions. The highest activity exhibited by a zirconium FI catalyst reached an astonishing catalyst turnover frequency (TOF) of 64,900 s ^–1 atm ^–1, which is two orders of magnitude greater than that seen with Cp₂ZrCl₂ under the same conditions. In addition, titanium FI catalysts with fluorinated ligands promote exceptionally high‐speed, living ethylene polymerization and can produce monodisperse high molecular weight polyethylenes (M_w/M_n<1.2, max. M_n>400,000) at 50 °C. The maximum TOF, 24,500 min ^–1 atm ^–1, is three orders of magnitude greater than those for known living ethylene polymerization catalysts. Moreover, the fluorinated FI catalysts promote stereospecific room‐temperature living polymerization of propylene to provide highly syndiotactic monodisperse polypropylene (max. [rr] 98%). The versatility of the FI catalysts allows for the creation of new polymers which are difficult or impossible to prepare using group 4 metallocene catalysts. For example, it is possible to prepare low molecular weight (M_v∼10³) polyethylene or poly(ethylene‐co‐propylene) with olefinic end groups, ultra‐high molecular weight polyethylene or poly(ethylene‐co‐propylene), high molecular weight poly(1‐hexene) with atactic structures including frequent regioerrors, monodisperse poly(ethylene‐co‐propylene) with various propylene contents, and a number of polyolefin block copolymers [e.g., polyethylene‐b‐poly(ethylene‐co‐propylene), syndiotactic polypropylene‐b‐poly(ethylene‐co‐propylene), polyethylene‐b‐poly(ethylene‐co‐propylene)‐b‐syndiotactic polypropylene]. These unique polymers are anticipated to possess novel material properties and uses.     

Analytical Electron Microscopy of Heterogeneous Catalysts

Abstract

Conventional transmission electron microscopy (CTEM) is by now a quite well-established technique for the study of heterogeneous catalysts. It is commonly used for the determination of metallic particles shapes and size distribution on various types of carriers [1, 2]. In addition, dark field imaging and diffraction measurements (in selected area or microdiffraction mode) allows advantage to be taken of the diffraction of the electrons in order to identify the active phase on the basis of its crystal structure [3, 4].     

Activated Carbon Monolith Catalysts (ACMC): A New and Novel Catalyst System

Monolithic catalysts have been widely used in gas–solid phase systems for a variety of environmental applications. More recently they are being investigated for use in three phase systems however there are few catalysts available commercially for these applications. Monoliths offer several advantages over traditional three phase slurry and trickle bed systems, in that they can be easily separated from the system, offer low pressure drop and high rates of adiabatic cooling, and are mostly linear when scaling up. In this chapter, we present a new and novel three phase catalyst, Activated Carbon Monolith Catalyst (ACMC), utilizing a newly developed integrated activated carbon monolith as an alternative to granular catalysts.     

Synthesis of Smectites and Porous Pillared Clay Catalysts: A Review

This paper reviews the synthesis of smectites and porous pillared clay catalysts. Synthetic as well as natural smectites serve as precursors for the synthesis of Al, Zr, Ti, Fe, Cr, Ga, V, Si, and other pillared clays as well as mixed Fe/Al, Ga/Al, Si/Al, Zr/Al and other mixed metal/Al pillared clays. The use of these pillared clays in some catalytic reactions is also briefly reviewed.